It is known to provide a displacement-type water craft which operates such that as the water craft moves through the water a mass of water is displaced from a front portion to a rear portion of the water craft.
At relatively low speed, the water craft is capable of moving relatively efficiently through a body of water. However, when the water craft moves relatively quickly through a body of water, the rate at which water is required to be displaced consequently increases which causes significant turbulence and a consequent loss of efficiency. This effect is increased when waves are encountered by the water craft since the water craft will cut relatively deep into the body of water when the water craft passes through a wave crest.
Furthermore, displacement-type water craft also tend to provide a passenger with an uncomfortable ride and an increased risk of sea sickness since the body of the water craft generally follows the surface of the water.
In order to overcome some of the disadvantages of displacement-type water craft, it is known to provide planing-type water craft which rise up relative to a body of water and plane across the surface of the body of water when the water craft attains sufficient speed. This allows the water craft to move much faster across the body of water using less energy than displacement-type water craft.
However, if the surface of the body of water is not relatively flat, an uncomfortable jarring motion occurs as a result of heavy impact between the water craft and each successive wave front. In relatively rough water, such planing-type water craft are unable to achieve planing speed and are compelled to move relatively slowly and inefficiently as displacement-type water craft.
A further alternative is to provide a water craft with two or more elongate narrow hulls which slice through the water more economically and more comfortably than relatively wide single hull water craft.
However, such multi hull-type water craft are prone to accident because they are of rigid construction; in some circumstances, for example in relatively rough conditions, at least one hull lifts from the water surface while the other hull(s) become submerged. As a consequence, extreme forces are localised within parts of the structure which can cause the craft to break or capsize.
In order to increase speed and comfort by reducing the contact surface area between the or each hull of the water craft and a body of water, hydrofoil-type water craft have been produced. With such hydrofoil-type water craft, submerged wings are provided such that when the water craft reaches a particular speed, the wings produce sufficient lift to raise the craft out of the water. Since the wings are completely submerged and cut through the water rather than travelling on the surface of the water, hydrofoil-type water craft require considerable engine power to raise the or each hull out of the body of water during use. In addition, the drag caused by the submerged wings causes the water craft to be very inefficient when moving slowly. Hydrofoil-type water craft are also unable to operate in relatively shallow waters as the wings and engine propellers tend to extend a few meters below the water surface when the water craft is moving slowly or is at rest.